Basic HTML version of Foils prepared March 30 97

Foil 4 Scalar Data I -- Numbers (Chapter 2 of Llama Book)

From PERL4 Tutorial for CPS616 Computational Science for Information Age Course CPS616 -- February 1995. by Geoffrey C. Fox


1 Scalars are either numbers or a string of characters as in C although in both cases there are significant if "second-order" differences
  • numbers and strings are not typed separately
  • Note Perl is "safer" than JavaScript in this regard and it is very rare that numbers and strings are confused
2 Numbers are stored internally as integers if this represents them adequately -- otherwise as double precision numbers
  • Perl and the runtime system make certain that this is transparent to user
  • Wolfram's SMP (the forerunner of Mathematica) at Caltech (which I worked on) also made the more extreme choice of everything being double precision
  • For example 1, 5.0, 4.5E23, and 7.45 E-15, are all numbers
3 Octal and Hexadecimal numbers are allowed with
  • O377 (initial zero) assumed to be Octal and so equal to 255 decimal
  • OX or Ox reprepresents hexadecimal with letters A to F corresponding to numbers 10 to 15 as normal. OXFF is hex FF or also 255 decimal

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