ABC QUICK REFERENCE

COMMANDS

WRITE expr: Write to screen; / before or after expr gives new line
READ address EG expr: Read expression from terminal to address; expr is example
READ address RAW: Read line of text
PUT expr IN address: Put value of expr in address
SET RANDOM expr: Start random sequence for random and choice
REMOVE expr FROM list: Remove one element from list
INSERT expr IN list: Insert in right place
DELETE address: Delete permanent location or table entry
PASS: Do nothing
KEYWORD expr KEYWORD ...: Execute user-defined command
KEYWORD: Execute refined command
CHECK: test Check test and stop if it fails
IF test: commands: If test succeeds, execute commands; no ELSE allowed
SELECT: test: commands ... test: commands: Select one alternative: try each test in order (one must succeed; the last test may be ELSE)
WHILE test: commands: As long as test succeeds execute commands
FOR name,... IN train: commands: Take each element of train in turn

QUIT: Leave command how-to or command refinement, or leave ABC
RETURN expr: Leave function how-to or expression refinement, return value of expr
REPORT test: Leave predicate how-to or test-refinement, report outcome of test
SUCCEED: The same, report success
FAIL: The same, report failure

x < y, x <= y, x >= y, x > y, x = y, x <> y, 0 <= d < 10: Order tests (<> means 'not equals')
pr, pr x, x pr y: Outcome of predicate pr (no permanent effects)
name: Outcome of refinement (no permanent effects)
test AND test AND ...: Fails as soon as one of the tests fails
test OR test OR ...: Succeeds as soon as one of the tests succeeds
NOT test
SOME name,... IN train HAS test: Sets name, ... on success
EACH name,... IN train HAS test: Sets name, ... on failure
NO name,... IN train HAS test: Sets name, ... on failure

~x: Approximate value of x
exactly x: Exact value of x
exact x: Test if x is exact
+x, x+y, x-y, -x, x*y, x/y: Plain arithmetic
x**y: x raised to the power y
root x, n root x: Square root, n-th root
abs x, sign x: Absolute value, sign (= -1, 0, or +1)
round x, floor x, ceiling x: Rounded to whole number
n round x: x rounded to n digits after decimal point
a mod n: Remainder of a on division by n
*/x: Numerator of exact number x
/*x: Denominator
random: Random approximate number r, 0 <= r < 1
e, exp x: Base of natural logarithm, exponential function
log x, b log x: Natural logarithm, logarithm to the base b
pi, sin x, cos x, tan x, arctan x: Trigonometric functions, with x in radians
angle (x, y), radius (x, y): Angle of and radius to point (x, y)
c sin x, c cos x, c tan x: Similar, with the circle divided into c parts
c arctan x, c angle (x, y): (e.g. 360 for degrees)
now: e.g. (1999, 12, 31, 23, 59, 59.999)

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