Computer Algebra I: Mathematica, SymPy, Sage, Maxima

a side-by-side reference sheet

mathematicasympysagemaxima
version used

10.0Python 2.7; SymPy 0.76.105.37
show version

select About Mathematica in Mathematica menusympy.__version__$sage --version also displayed on worksheet$ maxima --version
implicit prologuefrom sympy import *

# enable LaTeX rendering in Jupyter notebook:
init_printing()

# unknown variables must be declared:
x, y = symbols('x y')
# unknowns other than x must be declared:
y = var('y')
grammar and invocation
mathematicasympysagemaxima
interpreter

$cat > hello.m Print["Hello, World!"]$ MathKernel -script hello.m
if foo.py imports sympy:
$python foo.py$ cat > hello.sage
print("Hello, World!")

$sage hello.sage$ cat >> hello.max
print("Hello, world!");

$maxima -b hello.maxima repl$ MathKernel$python >>> from sympy import *$ sage$maxima block delimiters ( stmt; ): and offside rule: and offside ruleblock([x: 3, y: 4], x + y); /* Multiple stmts are separated by commas; a list of assignments can be used to set variables local to the block. */ statement separator; or sometimes newline A semicolon suppresses echoing value of previous expression. newline or ; newlines not separators inside (), [], {}, triple quote literals, or after backslash: \ newline or ; newlines not separators inside (), [], {}, triple quote literals, or after backslash: \ ; or$

The dollar sign $suppresses output. end-of-line comment none1 + 1 # addition1 + 1 # additionnone multiple line comment 1 + (* addition *) 1nonenone1 + /* addition */ 1; variables and expressions mathematicasympysagemaxima assignmenta = 3 Set[a, 3] (* rhs evaluated each time a is accessed: *) a := x + 3 SetDelayed[a, x + 3] a = 3a = 3a: 3; parallel assignment{a, b} = {3, 4} Set[{a, b}, {3, 4}] a, b = 3, 4a, b = 3, 4[a, b]: [3, 4] compound assignment+= -= *= /= corresponding functions: AddTo SubtractFrom TimeBy DivideBy += -= *= /= //= %= ^= **=+= -= *= /= //= %= **=none increment and decrement++x --x PreIncrement[x] PreDecrement[x] x++ x-- Increment[x] Decrement[x] nonenonenone non-referential identifierany unassigned identifier is non-referentialx, y, z, w = symbols('x y z w')y, z, w = var('y z w') # x is non-referential unless assigned a value any unassigned identifier is non-referential identifier as valuex = 3 y = HoldForm[x] x: 3; y: 'x; global variablevariables are global by defaultg1, g2 = 7, 8 def swap_globals(): global g1, g2 g1, g2 = g2, g1 g1, g2 = 7, 8 def swap_globals(): global g1, g2 g1, g2 = g2, g1 variables are global by default local variableModule[{x = 3, y = 4}, Print[x + y]] (* makes x and y read-only: *) With[{x = 3, y = 4}, Print[x + y]] (* Block[ ] declares dynamic scope *) assignments inside functions are to local variables by defaultassignments inside functions are to local variables by defaultblock([x: 3, y: 4], print(x + y)); null NullNoneNoneno null value null test x == Nullx is Nonex is Noneno null value undefined variable access treated as an unknown numberraises NameErrorraises NameErrortreated as an unknown number remove variable bindingClear[x] Remove[x] del xdel xkill(x); conditional expression If[x > 0, x, -x]x if x > 0 else -xx if x > 0 else -xif x < 0 then -x else x; arithmetic and logic mathematicasympysagemaxima true and false True FalseTrue FalseTrue Falsetrue false falsehoods FalseFalse 0 0.0False None 0 0.0 '' [] {} logical operators! True || (True && False) Or[Not[True], And[True, False]] Or(Not(True), And(True, False)) # when arguments are symbols: ~ x | (y & z) and or not relational expression1 < 2is(1 < 2); relational operators== != > < >= <= corresponding functions: Equal Unequal Greater Less GreaterEqual LessEqual Eq Ne Gt Lt Ge Le # when arguments are symbols: == != > < >= <= == != > < >= <== # > < >= <= arithmetic operators+ - * / Quotient Mod adjacent terms are multiplied, so * is not necessary. Quotient and Mod are functions, not binary infix operators. These functions are also available: Plus Subtract Times Divide + - * / ?? % if an expression contains a symbol, then the above operators are rewritten using the following classes: Add Mul Pow Mod + - * / // %+ - * / quotitent() mod() quotient and mod are functions, not binary infix operators. integer division Quotient[a, b]7 // 3quotient(7, 3); integer division by zerodividend is zero: Indeterminate otherwise: ComplexInfinity raises ZeroDivisionErrorerror float divisionexact division: a / b a / b float division by zerodividend is zero: Indeterminate otherwise: ComplexInfinity error power2 ^ 32 Power[2, 32] 2 ** 32 Pow(2, 32) 2 ^ 32 2 ** 32 2 ^ 32; 2 ** 32; sqrtreturns symbolic expression: Sqrt[2] sqrt(2)sqrt(2)sqrt(2); sqrt -1 III%i transcendental functionsExp Log Sin Cos Tan ArcSin ArcCos ArcTan ArcTan ArcTan accepts 1 or 2 arguments exp log sin cos tan asin acos atan atan2 exp log sin cos tan asin acos atan atan2 exp log sin cos tan asin acos atan atan2 transcendental constants π and Euler's number Pi E EulerGammapi Epi e euler_gamma%pi %e %gamma float truncation round towards zero, round to nearest integer, round down, round up IntegerPart Round Floor Ceilingfloor ceiling int round floor ceil truncate round floor ceiling absolute value and signum Abs SignAbs signabs signabs sign sign returns pos, neg, or zero integer overflow none, has arbitrary length integer typenone, has arbitrary length integer typenone, has arbitrary length integer typenone, has arbitrary length integer type float overflow nonenone rational construction2 / 7Mul(2, Pow(7, -1)) Rational(2, 7) 2 / 72 / 7 rational decomposition Numerator[2 / 7] Denominator[2 / 7] numer, denom = fraction(Rational(2, 7))numerator(2 / 7) denominator(2 / 7) num(2 / 7); denom(2 / 7); decimal approximationN[2 / 7] 2 / 7 + 0. 2 / 7 // N N[2 / 7, 100] N(Rational(2, 7)) N(Rational(2, 7), 100) n(2 / 7) n(2 / 7, 100) # synonyms for n: N(2 / 7) numerical_approx(2 / 7) 2 / 7, numer; complex construction 1 + 3I1 + 3 * I1 + 3 * I1 + 3 * %i; complex decomposition real and imaginary part, argument and modulus, conjugate Re Im Arg Abs Conjugate re im Abs arg conjugate (3 + I).real() (3 + I).imag() abs(3 + I) arg(3 + I) (3 + I).conjugate() realpart imagpart cabs carg conjugate random number uniform integer, uniform float RandomInteger[{0, 99}] RandomReal[] random(100); random(1.0); random seed set, get SeedRandom[17] ?? set_random_state(make_random_state(17)); ?? bit operatorsBitAnd[5, 1] BitOr[5, 1] BitXor[5, 1] BitNot[5] BitShiftLeft[5, 1] BitShiftRight[5, 1] none binary, octal, and hex literals2^^101010 8^^52 16^^2a ibase: 2; 101010; ibase: 8; 52; /* If first hex digit is a letter, prefix a zero: */ ibase: 16; 2a; radixBaseForm[42, 7] BaseForm[7^^60, 10] obase: 7; 42; to array of digits(* base 10: *) IntegerDigits[1234] (* base 2: *) IntegerDigits[1234, 2] strings mathematicasympysagemaxima string literal "don't say \"no\""use Python stringsuse Python strings"don't say \"no\"" newline in literal yesNewlines are inserted into strings by continuing the string on the next line. However, if the last character on a line inside a string is a backslash, the backslash and the following newline are omitted. literal escapes\\ \" \b \f \n \r \t \ooo\" \\ concatenate "one " <> "two " <> "three"concat("one ", "two ", "three"); translate caseToUpperCase["foo"] ToLowerCase["FOO"] supcase("foo"); sdowncase("FOO"); trim StringTrim[" foo "]strim(" ", " foo "); number to string "value: " <> ToString[8]concat("value: ", 8); string to number7 + ToExpression["12"] 73.9 + ToExpression[".037"] 7 + parse_string("12"); 73.9 + parse_string(".037"); /* parse_string raises error if the string does not contain valid Maxima code. Use numberp predicate to verify that the return value is numeric. */ string joinStringJoin[Riffle[{"foo", "bar", "baz"}, ","]]simplode(["foo", "bar", "baz"], ","); split StringSplit["foo,bar,baz", ","]split("foo,bar,baz", ","); substitute first occurrence, all occurences s = "do re mi mi" re = RegularExpression["mi"] StringReplace[s, re -> "ma", 1] StringReplace[s, re -> "ma"] ssubst("mi", "ma", "do re mi mi mi"); ssubstfirst("mi", "ma", "do re mi mi mi"); length StringLength["hello"]slength("hello"); index of substringStringPosition["hello", "el"][[1]][[1]] (* The index of the first character is 1.*) (* StringPosition returns an array of pairs, one for each occurrence of the substring. Each pair contains the index of the first and last character of the occurrence. *) ssearch("el", "hello"); /* 1 is index of first character; returns false if substring not found */ _ extract substring(* "el": *) StringTake["hello", {2, 3}] substring("hello", 2, 4); character literal nonenone character lookupCharacters["hello"][[1]] chr and ordFromCharacterCode[{65}] ToCharacterCode["A"][[1]] ascii(65); cint("A"); delete charactersrules = {"a" -> "", "e" -> "", "i" -> "", "o" -> "", "u" -> ""} StringReplace["disemvowel me", rules] arrays mathematicasympysagemaxima literal{1, 2, 3} List[1, 2, 3] use Python listsuse Python lists[1, 2, 3]; size Length[{1, 2, 3}]length([1, 2, 3]); lookup(* access time is O(1) *) (* indices start at one: *) {1, 2, 3}[[1]] Part[{1, 2, 3}, 1] a: [6, 7, 8]; a[1]; update a[[1]] = 7a[1]: 7; out-of-bounds behaviorleft as unevaluated Part[] expressionError for both lookup and update. element index(* Position returns list of all positions: *) First /@ Position[{7, 8, 9, 9}, 9] a: [7, 8, 9, 9]; first(sublist_indices(a, lambda([x], x = 9))); slice {1, 2, 3}[[1 ;; 2]] array of integers as index(* evaluates to {7, 9, 9} *) {7, 8, 9}[[{1, 3, 3}]] manipulate backa = {6,7,8} AppendTo[a, 9] elem = a[[Length[a]]] a = Delete[a, Length[a]] elem manipulate fronta = {6, 7, 8} PrependTo[a, 5] elem = a[[1]] a = Delete[a, 1] elem a: [6, 7, 8]; push(5, a); elem: pop(a); head First[{1, 2, 3}]first([1, 2, 3]); tail Rest[{1, 2, 3}]rest([1, 2, 3]); cons(* first arg must be an array *) Prepend[{2, 3}, 1] cons(1, [2, 3]); concatenate Join[{1, 2, 3}, {4, 5, 6}]append([1, 2, 3], [4, 5, 6]); replicate tenZeros = Table[0, {i, 0, 9}]ten_zeros: makelist(0, 10); copy a2 = aa2: copylist(a); iterate Do[Print[i], {i, {1, 2, 3}}]for i in [1, 2, 3] do print(i); reverse Reverse[{1, 2, 3}]reverse([1, 2, 3]); sort(* original list not modified: *) a = Sort[{3, 1, 4, 2}] sort([3, 1, 4, 2]); dedupe DeleteDuplicates[{1, 2, 2, 3}]unique([1, 2, 2, 3]); membership MemberQ[{1, 2, 3}, 2]member(7, {1, 2, 3}); evalb(7 in {1, 2, 3}); mapMap[Function[x, x x], {1, 2, 3}] Function[x, x x] /@ {1, 2, 3} (* if function has Listable attribute, Map is unnecessary: *) sqr[x_] := x * x SetAttributes[sqr, Listable] sqr[{1, 2, 3, 4}] map(lambda([x], x * x), [1, 2, 3]); filter Select[{1, 2, 3}, # > 2 &]sublist([1, 2, 3], lambda([x], x > 2)); reduce Fold[Plus, 0, {1, 2, 3}] universal and existential testsnone min and max elementMin[{6, 7, 8}] Max[{6, 7, 8}] apply(min, [6, 7, 8]); apply(max, [6, 7, 8]); shuffle and samplex = {3, 7, 5, 12, 19, 8, 4} RandomSample[x] RandomSample[x, 3] flatten one level, completely Flatten[{1, {2, {3, 4}}}, 1] Flatten[{1, {2, {3, 4}}}] /* completely: */ flatten([1, [2, [3, 4]]]); zip(* list of six elements: *) Riffle[{1, 2, 3}, {"a", "b", "c"}] (* list of lists with two elements: *) Inner[List, {1, 2, 3}, {"a", "b", "c"}, List] (* same as Dot[{1, 2, 3}, {2, 3, 4}]: *) Inner[Times, {1, 2, 3}, {2, 3, 4}, Plus] /* list of six elements: */ join([1, 2, 3], ["a", "b", "c"]); cartesian productOuter[List, {1, 2, 3}, {"a", "b", "c"}] sets mathematicasympysagemaxima literal(* same as arrays: *) {1, 2, 3} {1, 2, 3}{1, 2, 3}{1, 2, 3} sizeLength[{1, 2, 3}]len({1, 2, 3})len({1, 2, 3})cardinality({1, 2, 3}); array to setDeleteDuplicates[{1, 2, 2, 3}]set([1, 2, 3])set([1, 2, 3])setify([1, 2, 3]); set to arraynone; sets are arrayslist({1, 2, 3})list({1, 2, 3})listify({1, 2, 3}); membership test MemberQ[{1, 2, 3}, 7]7 in {1, 2, 3}7 in {1, 2, 3}elementp(7, {1, 2, 3}); subset testSubsetQ[{1, 2, 3}, {1, 2}]{1, 2} <= {1, 2, 3} {1, 2}.issubset({1, 2, 3}) {1, 2, 3} >= {1, 2} {1, 2, 3}.issuperset({1, 2}) {1, 2} <= {1, 2, 3} {1, 2}.issubset({1, 2, 3}) {1, 2, 3} >= {1, 2} {1, 2, 3}.issuperset({1, 2}) subsetp({1, 2}, {1, 2, 3}); universal and existential testsevery(lambda([x], x > 2), [1, 2, 3]); some(lambda([x], x > 2), [1, 2, 3]); unionUnion[{1, 2}, {2, 3, 4}]{1, 2, 3} | {2, 3, 4} {1, 2, 3}.union({2, 3, 4}) {1, 2, 3} | {2, 3, 4} {1, 2, 3}.union({2, 3, 4}) union({1, 2, 3}, {2, 3, 4}); intersection Intersect[{1, 2}, {2, 3, 4}]{1, 2, 3} & {2, 3, 4} {1, 2, 3}.intersection({2, 3, 4}) {1, 2, 3} & {2, 3, 4} {1, 2, 3}.intersection({2, 3, 4}) intersection({1, 2, 3}, {2, 3, 4}); relative complementComplement[{1, 2, 3}, {2}]{1, 2, 3} - {2, 3, 4} {1, 2, 3}.difference({2, 3, 4}) {1, 2, 3} - {2, 3, 4} {1, 2, 3}.difference({2, 3, 4}) setdifference({1, 2, 3}, {2, 3, 4}); powersetset(Set({1, 2, 3}).subsets())powerset({1, 2, 3}); cartesian productOuter[List, {1, 2, 3}, {"a", "b", "c"}]cartesian_product({1, 2, 3}, {"a", "b", "c"}); arithmetic sequences mathematicasympysagemaxima unit difference Range[1, 100]range(1, 101)range(1, 101)makelist(i, i, 1, 100); difference of 10 Range[1, 100, 10]range(1, 100, 10)range(1, 100, 10)makelist(i, i, 1, 100, 10); difference of 1/10 Range[1, 100, 1/10][1 + Rational(1,10)*i for i in range(0, 991)][1 + (1/10)*i for i in range(0, 991)]makelist(i, i, 1, 100, 1/10); dictionaries mathematicasympysagemaxima literal d = <|"t" -> 1, "f" -> 0|> (* or convert list of rules: *) d = Association[{"t" -> 1, "f" -> 0}] (* and back to list of rules: *) Normal[d] use Python dictionariesuse Python dictionariesd: [["t", 1], ["f", 0]]; size Length[Keys[d]]length(d); lookup d["t"]assoc("t", d); updated["f"] = -1d2: cons(["f", -1], sublist(d, lambda([p], p[1] # "f"))); missing key behavior Returns a symbolic expression with head "Missing". If the lookup key was "x", the expression is: Missing["KeyAbsent", "x"] assoc returns false is key present KeyExistsQ[d, "t"] iterate keys and values as arraysKeys[d] Values[d] map(lambda([p], p[1]), d); map(lambda([p], p[2]), d); sort by valuesSort[d] functions mathematicasympysagemaxima define functionAdd[a_, b_] := a + b (* alternate syntax: *) Add = Function[{a, b}, a + b] add(a, b) := a + b; define(add(a, b), a + b); /* block body: */ add(a, b) := block(print("adding", a, "and", b), a + b); /* square bracket syntax: */ I[row, col] := if row = col then 1 else 0; I[10, 10]; invoke functionAdd[3, 7] Add @@ {3, 7} (* syntax for unary functions: *) 2 // Log add(3, 7); boolean function attributes list, set, clear Attributes[add] SetAttributes[add, {Orderless, Flat, Listable}] ClearAtttibutes[add, Listable] undefine functionClear[Add]remfunction(add); redefine functionAdd[a_, b_] := b + aadd(a, b) := b + a; missing function behaviorThe expression is left unevaluated. The head is the function name as a symbol, and the parts are the arguments.The expression is left unevaluated. missing argument behaviorThe expression is left unevaluated. The head is the function name as a symbol, and the parts are the arguments.Too few arguments error. extra argument behaviorThe expression is left unevaluated. The head is the function name as a symbol, and the parts are the arguments.Too many arguments error. default argumentOptions[myLog] = {base -> 10} myLog[x_, OptionsPattern[]] := N[Log[x]/Log[OptionValue[base]]] (* call using default: *) myLog[100] (* override default: *) myLog[100, base -> E] return valuelast expression evaluated, or argument of Return[]last expression evaluated Inside a block(), the last expression evaluated or the argument of return() anonymous functionFunction[{a, b}, a + b] (#1 + #2) & f: lambda([x, y], x + y); f(3, 7); variable number of arguments(* one or more arguments: *) add[a__] := Plus[a] (* zero or more arguments: *) add[a___] := Plus[a] add([a]) := sum(a[i], i, 1, length(a)); pass array elements as separate argumentsApply[f, {a, b, c}] f @@ {x, y, z} a = [x, y, z] f(*a) add(a, b) := a + b; apply(add, [3, 7]); execution control mathematicasympysagemaxima ifIf[x > 0, Print["positive"], If[x < 0, Print["negative"], Print["zero"]]] use Python execution controluse Python execution controlif x > 0 then print("positive") else if x < 0 then print("negative") else print("zero"); whilei = 0 While[i < 10, Print[i]; i++] for i: 0 step 1 while i < 10 do print(i); forFor[i = 0, i < 10, i++, Print[i]]for i: 1 step 1 thru 10 do print(i); breakBreak[] continueContinue[] exceptions mathematicasympysagemaxima raise exceptionThrow["failed"]use Python exceptionsuse Python exceptionserror("failed"); handle exceptionPrint[Catch[Throw["failed"]]]errcatch(error("failed")); streams mathematicasympysagemaxima standard file handlesStreams["stdout"] Streams["stderr"] (* all open file handles: *) Streams[] write line to stdoutPrint["hello"] open file for readingf = OpenRead["/etc/hosts"] open file for writingf = OpenWrite["/tmp/test"] open file for appendingf = OpenAppend["/tmp/test"] close fileClose[f] read file into strings = ReadString[f] write stringWriteString[f, "lorem ipsum"] read file into array of stringss = Import["/etc/hosts"] a = StringSplit[s, "\n"] file handle position get, set f = StringToStream["foo bar baz"] StreamPosition[f] (* beginning of stream: *) SetStreamPosition[f, 0] (# end of stream: *) SetStreamPosition[f, Infinity] open temporary filef = OpenWrite[] path = Part[f, 1] files mathematicasympysagemaxima file exists test, regular file testFileExistsQ["/etc/hosts"] FileType["/etc/hosts"] == File file sizeFileByteCount["/etc/hosts"] is file readable, writable, executable last modification timeFileDate["/etc/hosts"] copy file, remove file, rename fileCopyFile["/tmp/foo", "/tmp/bar"] DeleteFile["/tmp/foo"] RenameFile["/tmp/bar", "/tmp/foo"] directories mathematicasympysagemaxima working directorydir = Directory[] SetDirectory["/tmp"] build pathnameFileNameJoin[{"/etc", "hosts"}] dirname and basenameDirectoryName["/etc/hosts"] FileBaseName["/etc/hosts"] absolute pathname(* file must exist; symbolic links are resolved: *) AbsoluteFileName["foo"] AbsoluteFileName["/foo"] AbsoluteFileName["../foo"] AbsoluteFileName["./foo"] AbsoluteFileName["~/foo"] glob pathsFunction[x, Print[x]] /@ FileNames["/tmp/*"] make directoryCreateDirectory["/tmp/foo.d"] recursive copyCopyDirectory["/tmp/foo.d", "/tmp/baz.d"] remove empty directoryDeleteDirectory["/tmp/foo.d"] remove directory and contentsDeleteDirectory["/tmp/foo.d", DeleteContents -> True] directory testDirectoryQ["/etc"] libraries and namespaces mathematicasympysagemaxima load libraryGet["foo.m"]load(grobner); reflection mathematicasympysagemaxima get function documentation?Tan Information[Tan] print(solve.__doc__) # in IJupyter: solve? help(solve) solve?describe(solve); ? solve; function optionsOptions[Solve] Options[Plot] function sourceimport inspect inspect.getsourcelines(integrate) query data typeHead[x]type(x)symbolp(x); numberp(7); stringp("seven"); listp([1, 2, 3]); list variables in scopeNames[$Context <> "*"]/* user defined variables: */
values;

/* user defined functions: */
functions;
________________________________________________________________________________________________________________________________________________________________________________________________________________

## version used

The version of software used to check the examples in the reference sheet.

## show version

How to determine the version of an installation.

## implicit prologue

Code assumed to have been executed by the examples in the sheet.

# Grammar and Invocation

## interpreter

How to execute a script.

mathematica:

The full path to MathKernel on Mac OS X:

/Applications/Mathematica.app/Contents/MacOS/MathKernel


## repl

How to launch a command line read-eval-print loop for the language.

## block delimiters

How blocks are delimited.

## statement separator

How statements are separated.

## end-of-line comment

Character used to start a comment that goes to the end of the line.

## multiple line comment

The syntax for a delimited comment which can span lines.

# Variables and Expressions

## assignment

How to perform assignment.

Mathematica, Sympy, and Pari/GP support the chaining of assignments. For example, in Mathematica one can assign the value 3 to x and y with:

x = y = 3


In Mathematica and Pari/GP, assignments are expressions. In Mathematica, the following code is legal and evaluates to 7:

(x = 3) + 4


In Mathematica, the Set function behaves identically to assignment and can be nested:

Set[a, Set[b, 3]]


## delayed assignment

How to assign an expression to a variable name. The expression is re-evaluated each time the variable is used.

mathematica:

GNU make also supports assignment and delayed assignment, but = is used for delayed assignment and := is used for immediate assignment. This is the opposite of how Mathematica uses the symbols.

The POSIX standard for make only has = for delayed assignment.

## parallel assignment

How to assign values in parallel.

Parallel assignment can be used to swap the values held in two variables.

## compound assignment

The compound assignment operators.

## increment and decrement

Increment and decrement operators which can be used in expressions.

## non-referential identifier

An identifier which does not refer to a value.

A non-referential identifier will usually print as a string containing its name.

Expressions containing non-referential identifiers will not be evaluated, though they may be simplified.

Non-referential identifiers represent "unknowns" or "parameters" when performing algebraic derivations.

## identifier as value

How to get a value referring to an identifier.

The identifier may be the name of a variable containing a value. But the value referring to the identifier is distinct from the value in the variable.

One may manipulate a value referring to an identifier even if it is not the name of a variable.

## global variable

How to declare a global variable.

## local variable

How to declare a local variable.

pari/gp:

There is my for declaring a local variable with lexical scope and local for declaring a variable with dynamic scope.

local can be used to change the value of a global as seen by any functions which are called while the local scope is in effect.

## null

The null literal.

## null test

How to test if a value is null.

## undefined variable access

What happens when an undefined variable is used in an expression.

## remove variable binding

How to remove a variable. Subsequent references to the variable will be treated as if the variable were undefined.

## conditional expression

A conditional expression.

# Arithmetic and Logic

## true and false

The boolean literals.

## falsehoods

Values which evaluate to false in a conditional test.

sympy:

Note that the logical operators Not, And and Or do not treat empty collections or None as false. This is different from the Python logical operators not, and, and or.

pari/gp:

A vector or matrix evaluates to false if all components evaluate to false.

## logical operators

The Boolean operators.

sympy:

In Python, &, |, and & are bit operators. SymPy has defined __and__, __or__, and __invert__ methods to make them Boolean operators for symbols, however.

## relational operators

The relational operators.

sympy:

The full SymPy names for the relational operators are:

sympy.Equality             # ==
sympy.Unequality           # !=
sympy.GreaterThan          # >=
sympy.LessThan             # <=
sympy.StrictGreaterThan    # >
sympy.StrictLessThan       # <


The SymPy functions are attatched to the relational operators ==, !=, for symbols … using the methods __eq__, __ne__, __ge__, __le__, __gt__, __lt__. The behavior they provide is similar to the default Python behavior, but when one of the arguments is a SymPy expression, a simplification will be attempted before the comparison is made.

## arithmetic operators

The arithmetic operators.

## integer division

How to compute the quotient of two integers.

## integer division by zero

The result of dividing an integer by zero.

## float division

How to perform float division, even if the arguments are integers.

## float division by zero

The result of dividing a float by zero.

## power

How to compute exponentiation.

Note that zero to a negative power is equivalent to division by zero, and negative numbers to a fractional power may have multiple complex solutions.

## sqrt

The square root function.

For positive arguments the positive square root is returned.

## sqrt -1

How the square root function handles negative arguments.

mathematica:

An uppercase I is used to enter the imaginary unit, but Mathematica displays it as a lowercase i.

## transcendental functions

The standard transcendental functions such as one might find on a scientific calculator.

The functions are the exponential (not to be confused with exponentiation), natural logarithm, sine, cosine, tangent, arcsine, arccosine, arctangent, and the two argument arctangent.

## transcendental constants

The transcendental constants pi and e.

The transcendental functions can used to computed to compute the transcendental constants:

pi = acos(-1)
pi = 4 * atan(1)
e = exp(1)


## float truncation

Ways to convert a float to a nearby integer.

## absolute value

How to get the absolute value and signum of a number.

## integer overflow

What happens when the value of an integer expression cannot be stored in an integer.

The languages in this sheet all support arbitrary length integers so the situation does not happen.

## float overflow

What happens when the value of a floating point expression cannot be stored in a float.

## rational construction

How to construct a rational number.

## rational decomposition

How to extract the numerator and denominator from a rational number.

## decimal approximation

How to get a decimal approximation of an irrational number or repeating decimal rational.

## complex construction

How to construct a complex number.

## complex decomposition

How to extract the real and imaginary part from a complex number; how to extract the argument and modulus; how to get the complex conjugate.

## random number

How to generate a random integer or a random float.

pari/gp:

When the argument of random() is an integer n, it generates an integer in the range $$\{0, ..., n - 1\}$$ .

When the argument is a arbitrary precision float, it generates a value in the range [0.0, 1.0]. The precision of the argument determines the precision of the random number.

## random seed

How to set or get the random seed.

mathematica:

The seed is not set to the same value at start up.

## binary, octal, and hex literals

Binary, octal, and hex integer literals.

mathematica:

The notation works for any base from 2 to 36.

Convert a number to a representation using a given radix.

## to array of digits

Convert a number to an array of digits representing the number.

# Strings

## string literal

The syntax for a string literal.

## newline in literal

Are newlines permitted in string literals.

## literal escapes

Escape sequences for putting unusual characters in string literals.

## concatenate

How to concatenate strings.

## translate case

How to convert a string to all lower case letters or all upper case letters.

## trim

How to remove whitespace from the beginning or the end of string.

## number to string

How to convert a number to a string.

## string to number

How to parse a number from a string.

## string join

How to join an array of strings into a single string, possibly separated by a delimiter.

## split

How to split a string in to an array of strings. How to specify the delimiter.

## substitute

How to substitute one or all occurrences of substring with another.

## length

How to get the length of a string in characters.

## index of substring

How to get the index of the first occurrence of a substring.

## extract substring

How to get a substring from a string using character indices.

## character literal

The syntax for a character literal.

## character lookup

How to get a character from a string by index.

## chr and ord

Convert a character code point to a character or a single character string.

Get the character code point for a character or single character string.

## delete characters

Delete all occurrences of a set of characters from a string.

# Arrays

sectionmathematicamaplemaximasympy
arraysListlistlistlist
multidimensional arraysListArrayarraynone
vectorsListVectorlistMatrix
matricesListMatrixmatrixMatrix

## literal

The notation for an array literal.

## size

The number of elements in the array.

## lookup

How to access an array element by its index.

## update

How to change the value stored at an array index.

## out-of-bounds behavior

What happens when an attempt is made to access an element at an out-of-bounds index.

## element index

How to get the index of an element in an array.

## slice

How to extract a subset of the elements. The indices for the elements must be contiguous.

## copy

How to copy an array. Updating the copy will not alter the original.

## membership

How to test whether a value is an element of a list.

## intersection

How to to find the intersection of two lists.

## union

How to find the union of two lists.

## relative complement, symmetric difference

How to find all elements in one list which are not in another; how to find all elements which are in one of two lists but not both.

## shuffle and sample

How to shuffle an array. How to extract a random sample from an array without replacement.

## zip

How to interleave two arrays.

# Execution Control

## if

How to write a branch statement.

mathematica:

The 3rd argument (the else clause) of an If expression is optional.

## while

How to write a conditional loop.

mathematica:

Do can be used for a finite unconditional loop:

Do[Print[foo], {10}]


## for

How to write a C-style for statement.

## break/continue

How to break out of a loop. How to jump to the next iteration of a loop.

# Exceptions

## raise exception

How to raise an exception.

## handle exception

How to handle an exception.

## uncaught exception behavior

gap:

Calling Error() invokes the GAP debugger, which is similar to a Lisp debugger. In particular, all the commands available in the GAP REPL are still available. Variables can be inspected and modified while in the debugger but any changes will be lost when the debugger is quitted.

One uses quit; or ^D to exit the debugger. These commands also cause the top-level GAP REPL exit if used while not in a debugger.

If Error() is invoked while in the GAP debugger, the debugger will be invoked recursively. One must use quit; for each level of debugger recursion to return to the top -level GAP REPL.

Use

brk> Where(4);


to print the top four functions on the stack when the error occurred. Use DownEnv() and UpEnv() to move down the stack—i.e. from callee to caller—and UpEnv() to move up the stack. The commands take the number of levels to move down or up:

brk> DownEnv(2);
brk> UpEnv(2);


When the debugger is invoked, it will print a message. It may give the user the option of providing a value with the return statement so that a computation can be continued:

brk> return 17;


## finally block

How to write code that executes even if an exception is raised.

# Reflection

## function documentation

How to get the documentation for a function.

# Maple

http://www.maplesoft.com/support/help/

# Maxima

http://maxima.sourceforge.net/docs/manual/maxima.html

# Sage

http://doc.sagemath.org/html/en/index.html

# SymPy

Welcome to SymPy’s documentation!