Simple expressions, Python Programming

Simple expressions

A cornerstone of a programming language is the  ability  to compute expressions.  We will start here  with  arithmetic expressions, just to take the  concept.   An expression consists  of a sequence of 'tokens' that show the application of operators to data component. Each expression has a number,  which  may be computed recursively by evaluating primitive expressions, and then using  standard principles to combine their values  to get new variables. Numerals, such -3.7 as or 6  are expressions, whose  numbers  are  numeric constants. Their numeric values  can be integers, within some  range  dictated by the  programming language, or ?oating point  variables. Floating  point  variables are used  to represent non-integer values,  but they  are not related, in many  important types,  from  the  real  numbers.  There  are in?nitely many real numbers within a ?nite  difference, but  only  finite various  ?oating-point numbers exist at all.  In fact, the normal laws of real arithmetic (transitivity, associativity, etc.)  are created in ?oating-point arithmetic, because  the results of any provided sub-computation may not be representable in the given number of bits.

 

We will explain the calculation of expressions in Python by showing short  transcripts of interactive sessions  with the Python shell : the shell is a computer program that

  • Prompts the user for a relation, by typing »>,
  • Reads what the user types in, and changes it into a set of tokens,
  • Parses the tokens into a data structure showing the syntax of the expression,
  • Computes the parsed expression using an interpreter, and
  • Prints out the resulting value

 

So, for example, we might  have this interaction with Python:

>>> 2 + 3

5

>>> (3 * 8) - 2

22

>>> ((3 * 8) - 2) / 11

2

>>> 2.0

2.0

>>> 0.1

0.10000000000000001

>>> 1.0 / 3.0

0.33333333333333331

>>> 1 / 3

0

There are a couple  of things  to look here.  First, we can look how  ?oating point  values only approximately represent real numbers: when  we write in 0.1, the closest Python can take it in ?oating point  is 0.100000000000001.  The end interaction is particularly troubling: it seems like the value of the expression 1 / 3 should be something like 0.3333.  However, in Python, if both registers to the / operator are integer number, then it will operate an integer division.

 

These expressions can be arbitrarily deeply nested combinations of primitives. The laws used  for calculation are essentially the same as the ones you learned in school; the interpreter proceeds by applying the operations in precedence order13,  calculating sub-expressions to get new variables,  and then calculating the expressions those values  takes in, until in one value  results.

 

Posted Date: 8/11/2012 1:32:28 AM | Location : United States







Related Discussions:- Simple expressions, Assignment Help, Ask Question on Simple expressions, Get Answer, Expert's Help, Simple expressions Discussions

Write discussion on Simple expressions
Your posts are moderated
Related Questions
simple program using list

Use the function to compute and print the sum of first n prime numbers.

Procedures in python Procedures are computer program creates that let us capture common patterns of computation by: Grouping together sequences of statements

what is python

Range Very frequently, we will want to iterate through a list of integer values, often as indices.  Python gives a useful function, range, which gives lists of integers. It ma

Suppose the cover price of a book is $24.95, but bookstores get a 40% discount. Shipping costs $3 for the first copy and 75 cents for each additional copy. What is the tota

Write an algorithm for a program that shows the use of all 6 math functions. Write, test, and debug the program using Python. SAMPLE OUTPUT (not including author/program infor

Variables We cannot  go very far without variables. A variable is a value related to a name that we can bind  to have a particular value  and  then  later use in an expression.

What are squared matrices?

how to make a python programme for van der waals equation of state with surface discontinouty