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55 lines
1.2 KiB
Plaintext
55 lines
1.2 KiB
Plaintext
NAME
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. - oldvalue
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SYNOPSIS
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. (with no adjacent letters or digits or _ or .)
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TYPES
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return any
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DESCRIPTION
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The "old value" is essentially a global variable with identifier "."
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which at top level when directly from a file or keyboard
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is automatically assigned the saved value for a line
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of statements when evaluation of that line is completed and this saved
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value is not null. A line of statements is normally completed by a
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'\n' not within a block bounded by braces or an expression bounded by
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parentheses.
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Disabling of saving by calling saveval(0) causes lines to return a
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null value and . then becomes in effect a global variable whose
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value may be changed by assignments and operations like ++ and --.
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A null value may be assigned to . by . = null() or free(.).
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EXAMPLE
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> saveval(1);
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> a = 2
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> .
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2
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> . += 3; b = . + 4
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> print ., b
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9 9
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> . += 3; b = . + 4; null()
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> print ., b
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12 16
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> list(a, b, a + b)
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list (3 elements, 3 nonzero):
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[[0]] = 2
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[[1]] = 16
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[[2]] = 18
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> saveval(0)
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> print pop(.), .[[1]]
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2 18
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LIMITS
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none
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LIBRARY
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none
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SEE ALSO
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saveval
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