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Article contents:== CHICKEN for Python programmers [[toc:]] == Hello, world! === Python <enscript highlight=python> print "Hello, world!" </enscript> === CHICKEN <enscript highlight=scheme> (print "Hello, world!") </enscript> == Definitions, assignment and bindings === Python Python has only one operator for both assignments and definitions of variables ({{=}}). <enscript highlight=python> a = 0 </enscript> === CHICKEN Defining a variable: <enscript highlight=scheme> (define a 0) </enscript> Assigning a variable a value: <enscript highlight=scheme> (set! a 0) </enscript> PS: CHICKEN automatically defines a global variable when a variable is set without being defined. However, it is best practice (and most compatible with other Schemes) to define all variables. Binding a value to a variable: <enscript highlight=scheme> (let ((a 0)) a) </enscript> == Strings === Concatenating ==== Python <enscript highlight=python> a = "1" + "2" </enscript> <enscript highlight=python> a = "".join(["1", "2"]) </enscript> <enscript highlight=python> a = sum(["1", "2"], start="") </enscript> ==== CHICKEN <enscript highlight=scheme> (string-append "1" "2") </enscript> <enscript highlight=scheme> (import (chicken string)) (conc "1" "2") </enscript> <enscript highlight=scheme> (import (chicken string)) ;; If you hadn't already (string-intersperse '("1" "2") "") </enscript> === Splitting a string ==== Python <enscript highlight=python> "this is a string".split() </enscript> ==== CHICKEN <enscript highlight=scheme> (import (chicken string)) ;; If you hadn't already (string-split "this is a string") </enscript> == File I/O === Reading the contents of a file and returning a string ==== Python <enscript highlight=python> open("my-file.txt").read() # Deprecated </enscript> <enscript highlight=python> with open("my-file.txt") as f: f.read() </enscript> ==== CHICKEN <enscript highlight=scheme> (import (chicken io)) (call-with-input-file "my-file.txt" (lambda (port) (read-string #f port))) </enscript> {{read-string}} is defined in [[/man/5/Module (chicken io)|the (chicken io) module]]. This module is not loaded by default, so we import it first. {{call-with-input-file}} calls its argument procedure with the opened file as an argument. The first argument to {{read-string}} is the limit, which tells it how many characters to read. We use {{#f}} to indicate we want to read everything (no limit). === Reading the contents of a file and returning a list of lines ==== Python <enscript highlight=python> open("my-file.txt").readlines() </enscript> <enscript highlight=python> with open("my-file.txt") as f: f.readlines() </enscript> ==== CHICKEN <enscript highlight=scheme> (import (chicken io)) (call-with-input-file "my-file.txt" (lambda (port) (read-lines port))) </enscript> {{read-lines}} is also defined in [[/man/5/Module (chicken io)|the (chicken io) module]]. == Conditionals === Single condition ==== Python <enscript highlight=python> "yes" if 1<2 else "no" </enscript> ==== CHICKEN <enscript highlight=scheme> (if (< 1 2) "yes" "no") </enscript> PS: in Scheme, the result of the evaluation of an {{if}} form returns the value of the arm that was taken, just as in the shorthand if form of Python. You can see this by the fact that the interpreter prints back the string, which is the value of the entire expression. === Multiple conditions ==== Python <enscript highlight=python> result = None if 1 < 2: result = "1 < 2" elif 1 > 2: result = "1 > 2" else: result = "1 = 2" </enscript> ==== CHICKEN <enscript highlight=scheme> (cond ((< 1 2) "1 < 2") ((> 1 2) "1 > 2") (else "1 = 2")) </enscript> PS: in Scheme, the result of the evaluation of a {{cond}} form is also the value of the expression in the arm that was taken. == Iteration === Iterating through and printing the elements of a list ==== Python <enscript highlight=python> l = [1, 2, 3, 4] for i in l: print i </enscript> ==== CHICKEN <enscript highlight=scheme> (define l '(1 2 3 4)) (for-each print l) </enscript> === Applying a procedure/function to each item of a list ==== Python <enscript highlight=python> l = [1, 2, 3, 4] def add10(n): return n + 10 [ add10(i) for i in l ] </enscript> ==== CHICKEN <enscript highlight=scheme> (define l '(1 2 3 4)) (define (add10 n) (+ n 10)) (map add10 l) </enscript> == Other references Other interesting reads to check out: * Michele Simionato's blog series [[http://www.artima.com/weblogs/viewpost.jsp?thread=251474|"The Adventures of a Pythonista in Schemeland"]] * Jack Trades' [[http://plr.sourceforge.net/cgi-bin/plr/launch.py|language comparison table]] ("Pointless Programming Reference") Description of your changes:

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