abstract

The concern is documenting the meaning and personal appropriation (wrapping my head around) the term “scalar” encountered in an intro course for Python.

contents

1. On scalars

1.1. define

The term “scalar” comes from linear algebra, where it is used to differentiate a single number from a VECTOR or MATRIX. The meaning in computing is similar. It distinguishes a single value like an integer or float from a data structure like an array. This distinction is very prominent in Perl In Perl, the $ sigil (which resembles an ‘s’) is used to denote a scalar variable — while @ sigil (which resembles an ‘a’) denotes an array It doesn’t have anything to do with the type of the element itself. It could be a number, character, string, or object What matters to be called a scalar is that there is ONE OF THEM.

— From https://softwareengineering.stackexchange.com/questions/238033/what-does-it-mean-when-data-is-scalar

1.2. compare

  • in Javascript, scalar types - types that only scale — are called primitives; and the opposite is called objects
  • in Perl, you have the opposite of scalars $ and arrays @
  • in Python the opposite of a scalar is not an array, nor a vector, but a collection
  • in SQL, a scalar value is 1-value result & a scalar subquery expression is a subquery that returns exactly oe column value from one row

1.3. find-origins

  • etymologically it seems to came from “scala” — a ladder in latin and the first usage in English as per Wiki is

came with W. R. Hamilton in 1846, referring to the real part of a quaternion: “The algebraically real part may receive, according to the question in which it occurs, all values contained on the one scale of progression of numbers from negative to positive infinity; we shall call it therefore the scalar part.”

  • to me than scalar means the constraint of modification for this type — it only “scales” and each binding is immutable; you can’t modify one of its parts

2. the illustration of python scalars: int, float, none, bool

2.1. init

  • unlimited precision signed int
  • in REPL, can be
    • decimal
    • binary with 0b prefix
    • octal with 0o prefix
    • hex with 0x prefix
  • rounding is always towards 0
>>> int(-3.5)
-3
>>> int(3.5)
3
>>>   
  • the int constructor also converts strings to ints
>>> int("365")
365

2.2. float

  • implemented as IEEE-754 double-precision with 53-bits of binary precision
  • between 15-16 significant digits
  • decimal point defines float
  • scientific notation can be used
>>> 3e8
300000000.0
  • use float constructor to cast into float
  • every calculation between float and an int is promoted to a float

2.3. None

noRepl_and_bindable

2.4. Bool

  • True
  • False
  • Bool constructor for casting truthy and falsy values into a bool

3. sources