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Arrays (Chapter 5)
• Definition
• Applications
• One-Dimensional
– Declaration
– Initialization
– Use
• Multidimensional
Declaration
#define SIZE 10
int main(void)
{
float sample[SIZE];
Initialization
#define SIZE 10
int main(void)
{
float sample[SIZE] = {5.0, 1.2,
-4.6, -7.5, 8.9, -1.0, 12.7,
0.0, 6.6, 4.2};
Gotchas
• First element of array is [0]
• Last element of array is [n-1] (major source of bugs!)
• No bounds check (MAJOR source of impossible-tofind bugs!)
Amino Acids
• I like this problem, but I don't especially like the way
the book does it.
• The book isn't careful enough about range errors.
• We can use a table-driven approach to looking up the
atomic weights of the elements. This takes more
space (bad), less time (good) than the way the book
looks up the weights. Also less opportunity for bugs
(very, very good).
Background
• Amino Acid: Organic molecule composed of carbon,
hydrogen, nitrogen, oxygen, sulfur.
• Building blocks of proteins.
• Amino acids are what DNA codes for.
• Weight is sum of weights of component atoms
Syntax
• One amino acid formula on a single line
• Amino acid formula consists of sequence of atom
counts
• Atom count is a letter specifying the atom, maybe
followed by a number specifying how many of them.
• O2C3NH7\n
Semantics
• O2C3NH7\n
– Two Oxygen (2.0 * 15.9994 = 31.9988)
Semantics
• O2C3NH7\n
– Two Oxygen (2.0 * 15.9994 = 31.9988)
– Three Carbon (3.0 * 12.011 = 36.033)
Semantics
• O2C3NH7\n
– Two Oxygen (2.0 * 15.9994 = 31.9988)
– Three Carbon (3.0 * 12.011 = 36.033)
– One Nitrogen (14.00674)
Semantics
• O2C3NH7\n
–
–
–
–
Two Oxygen (2.0 * 15.9994 = 31.9988)
Three Carbon (3.0 * 12.011 = 36.033)
One Nitrogen (14.00674)
Seven Hydrogen (7.0 * 1.00794 = 7.05558)
Semantics
• O2C3NH7\n
–
–
–
–
Two Oxygen (2.0 * 15.9994 = 31.9988)
Three Carbon (3.0 * 12.011 = 36.033)
One Nitrogen (14.00674)
Seven Hydrogen (7.0 * 1.00794 = 7.05558)
• Total: 31.9988 + 36.033 + 14.00674 + 7.05558 =
89.09412
Parsing
O2C3NH7\n
• Find new atoms (letters)
Parsing
O2C3NH7\n
• Find new atoms (letters)
– Look up atomic weight of atom (12.011)
Parsing
O2C3NH7\n
• Find new atoms (letters)
– Look up atomic weight of atom (12.011)
• Count how many we've got (numbers)
Parsing
O2C3NH7\n
• Find new atoms (letters)
– Look up atomic weight of atom (12.011)
• Count how many we've got (numbers)
–3
Parsing
O2C3NH7\n
• Find new atoms (letters)
– Look up atomic weight of atom (12.011)
• Count how many we've got (numbers)
–3
• When we reach next atom, add previous to atomic
weight of molecule
Parsing
O2C3NH7\n
• Find new atoms (letters)
– Look up atomic weight of atom (12.011)
• Count how many we've got (numbers)
–3
• When we reach next atom, add previous to atomic
weight of molecule
– 3*12.011 = 36.033
Look Up Atomic Weight
Look Up Atomic Weight
Look Up Atomic Weight
Counting
numatoms = numatoms * 10.0 +
newdigit;
Counting
numatoms = numatoms * 10.0 +
newdigit;
123
Counting
numatoms = numatoms * 10.0 +
newdigit;
123
0*10 + 1 = 1
Counting
numatoms = numatoms * 10.0 +
newdigit;
123
1*10 + 2 = 12
Counting
numatoms = numatoms * 10.0 +
newdigit;
123
12*10 + 3 = 123
Special Cases
• First letter: make sure we don't put gibberish in
molecular weight
• End of string: make sure we account for last atom
• If user didn't enter number for an atom, it means '1'
Writing the code
• Write initialization, input, core loop, output
• Handle special cases
• Error checking