Info Catalog calc: Quick Calculator calc: Introduction calc: Undo

calc: Prefix Arguments

 
 4.7 Numeric Prefix Arguments
 ============================
 
 Many Calculator commands use numeric prefix arguments.  Some, such as ‘d
 s’ (‘calc-sci-notation’), set a parameter to the value of the prefix
 argument or use a default if you don’t use a prefix.  Others (like ‘d f’
 (‘calc-fix-notation’)) require an argument and prompt for a number if
 you don’t give one as a prefix.
 
    As a rule, stack-manipulation commands accept a numeric prefix
 argument which is interpreted as an index into the stack.  A positive
 argument operates on the top N stack entries; a negative argument
 operates on the Nth stack entry in isolation; and a zero argument
 operates on the entire stack.
 
    Most commands that perform computations (such as the arithmetic and
 scientific functions) accept a numeric prefix argument that allows the
 operation to be applied across many stack elements.  For unary
 operations (that is, functions of one argument like absolute value or
 complex conjugate), a positive prefix argument applies that function to
 the top N stack entries simultaneously, and a negative argument applies
 it to the Nth stack entry only.  For binary operations (functions of two
 arguments like addition, GCD, and vector concatenation), a positive
 prefix argument “reduces” the function across the top N stack elements
 (for example, ‘C-u 5 +’ sums the top 5 stack entries; Reducing and
 Mapping), and a negative argument maps the next-to-top N stack
 elements with the top stack element as a second argument (for example,
 ‘7 c-u -5 +’ adds 7 to the top 5 stack elements).  This feature is not
 available for operations which use the numeric prefix argument for some
 other purpose.
 
    Numeric prefixes are specified the same way as always in Emacs: Press
 a sequence of <META>-digits, or press <ESC> followed by digits, or press
 ‘C-u’ followed by digits.  Some commands treat plain ‘C-u’ (without any
 actual digits) specially.
 
    You can type ‘~’ (‘calc-num-prefix’) to pop an integer from the top
 of the stack and enter it as the numeric prefix for the next command.
 For example, ‘C-u 16 p’ sets the precision to 16 digits; an alternate
 (silly) way to do this would be ‘2 <RET> 4 ^ ~ p’, i.e., compute 2 to
 the fourth power and set the precision to that value.
 
    Conversely, if you have typed a numeric prefix argument the ‘~’ key
 pushes it onto the stack in the form of an integer.
 

Info Catalog calc: Quick Calculator calc: Introduction calc: Undo