Held: Tuesday, 4 February 2003
Summary: Today we begin to learn how to tell Scheme to make decisions. The procedures used to make decisions are called conditionals. Today's class will be a large group design effort rather than an individual or small group design effort.
if. For example,
if the grade is at least 94, then give the student an A, otherwise, if the grade is between 90 and 93, ...
(if condition success-expression failure-expression)
ifdoes not behave according to the standard pattern, in which all the arguments to a procedure are computed before the procedure is applied).
(if (<= 90 grade) 'A 'F)
(if (<= 90 garde) 'A (if (<= 80 grade 89) 'B (if (<= 70 grade 79) ...)))
(if (<= grade 90) 'A (if (<= 80 grade) 'B (if (<= 70 grade) ...)))
cond, which more closely resembles a table.
condexpression looks like
(cond ((condition1) exp1) ((condition2) exp2) ((condition3) exp3) ... (else default-exp))
(cond ((<= 90 grade) 'A) ((<= 80 grade) 'B) ...)
#t) or false (
<(strictly less than),
<=(less than or equal to),
>=(greater than or equal to), and
>(strictly greater than).
Thursday, 16 January 2003 [Samuel A. Rebelsky]
Tuesday, 4 February 2003 [Samuel A. Rebelsky]
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