1 ! Copyright (C) 2009 Philipp Brüschweiler
2 ! See http://factorcode.org/license.txt for BSD license.
3 USING: help.syntax help.markup math prettyprint locals sequences ;
7 { $syntax "[infix ... infix]" }
8 { $description "Parses the infix code inside the brackets, converts it to stack code and executes it." }
11 "USING: infix prettyprint ;"
13 "[infix 8+2*3 infix] ."
16 { $link POSTPONE: [infix } " isn't that useful by itself, as it can only access literal numbers and no variables. It is designed to be used together with locals; for example with " { $link POSTPONE: :: } " :"
18 "USING: infix locals math.functions prettyprint ;"
20 ":: quadratic-equation ( a b c -- z- z+ )"
21 " [infix (-b-sqrt(b*b-4*a*c)) / (2*a) infix]"
22 " [infix (-b+sqrt(b*b-4*a*c)) / (2*a) infix] ;"
23 "1 0 -1 quadratic-equation . ."
29 { $syntax "[infix| binding1 [ value1... ]\n binding2 [ value2... ]\n ... |\n infix-expression infix]" }
30 { $description "Introduces a set of lexical bindings and evaluates the body as a snippet of infix code. The values are evaluated in parallel, and may not refer to other bindings within the same " { $link POSTPONE: [infix| } " form, as it is based on " { $link POSTPONE: [let } "." }
33 "USING: infix prettyprint ;"
35 "[infix| pi [ 3.14 ] r [ 12 ] | r*r*pi infix] ."
40 { POSTPONE: [infix POSTPONE: [infix| } related-words
42 ARTICLE: "infix" "Infix notation"
43 "The " { $vocab-link "infix" } " vocabulary implements support for infix notation in Factor source code."
49 "The usual infix math operators are supported:"
55 { { $snippet "%" } ", which is the infix operator for " { $link mod } "." }
57 "The standard precedence rules apply: Grouping with parentheses before " { $snippet "*" } ", " { $snippet "/" } "and " { $snippet "%" } " before " { $snippet "+" } " and " { $snippet "-" } "."
60 "[infix 5-40/10*2 infix] ."
64 "You can call Factor words in infix expressions just as you would in C. There are some restrictions on which words are legal to use though:"
66 "The word must return exactly one value."
67 "The word name must consist of the letters a-z, A-Z, _ or 0-9, and the first character can't be a number."
70 "USING: infix locals math.functions ;"
71 ":: binary_entropy ( p -- h )"
72 " [infix -(p*log(p) + (1-p)*log(1-p)) / log(2) infix] ;"
73 "[infix binary_entropy( sqrt(0.25) ) infix] ."
77 "You can access " { $vocab-link "sequences" } " inside infix expressions with the familiar " { $snippet "arr[index]" } " notation."
79 "USING: arrays infix ;"
80 "[infix| myarr [ { 1 2 3 4 } ] | myarr[4/2]*3 infix] ."
83 "Please note: in Factor " { $emphasis "fixnums are sequences too." } " If you are not careful with sequence accesses you may introduce subtle bugs:"
85 "USING: arrays infix locals ;"
86 ":: add-2nd-element ( x y -- res )"
87 " [infix x[1] + y[1] infix] ;"
88 "{ 1 2 3 } 5 add-2nd-element ."